1. Field of Invention
This invention relates to polymer films. More particularly, this invention relates to ultrathin, polyphenylene oxide polymer films and their production.
2. Prior Art
The preparation of polyphenylene oxide polymer films on a liquid support, such as water, is known. For example, U.S. Pat. No. 3,551,244 discloses a process for preparing polyphenylene oxide films on a water surface having thicknesses between 0.05 and 5.0 microns (i.e. between 500 and 50,000 angstroms). The patent lists several halogenated solvents, such as chloroform, which can be used for casting polyphenylene oxide films. However, no specific solvent mixtures and ratios suitable for casting ultrathin, pinhole-free, polyphenylene oxide films are disclosed.
In U.S. Pat. Nos. 3,257,358, 3,306,874 and 3,306,875, polyphenylene oxide films are disclosed. However, no film thicknesses are provided.
U.S. Pat. No. 3,933,561 discloses a process for producing polymer films having thicknesses of less than one micron (i.e. 10,000 angstroms), eg. 0.1 micron (i.e. 1,000 angstroms). Polyphenylene oxide is listed as a suitable polymer for the process. The preferred casting surface is water, and the term "water," as used in the patent, includes aqueous solutions containing inorganic acids. However, aqueous ortho-phosphoric acid is not disclosed as a suitable casting surface for pinhole-free, ultrathin, polyphenylene oxide films having thicknesses of 400 angstroms or less nor is a suitable solvent mixture for such films described.
U.S. Pat. Nos. 4,155,793, 4,279,855 and 4,374,891 disclose a process for casting on water substantially void-free, ultrathin, permeable, polymeric membranes having thicknesses of 500 angstroms or less. Films prepared from organopolysiloxane-polycarbonate interpolymers mixed with polyphenylene oxide in a 1:1 ratio by volume of trichloroethylene:trichloropropane are also disclosed. However, unmixed polyphenylene oxide films are not disclosed nor is a suitable casting surface for ultrathin, pinhole-free, polyphenylene oxide films having thicknesses of 400 angstroms or less described.
Other patents, such as U.S. Pat. Nos. 2,631,334, 2,689,187, and 4,393,113, also disclose ultrathin polymeric films. However polyphenylene oxide films are not disclosed.
In the prior art, the preparation of pinhole-free, ultrathin, polyphenylene oxide, free-standing films with thicknesses of less than 400 angstroms generally has not been disclosed. Usually, prior art polymer films with thicknesses of less than 400 angstroms that are cast contain holes or other macroscopic defects.
Accordingly, it is an object of this invention to prepare ultrathin, polyphenylene oxide polymer films.
It is a further object of this invention to prepare pinhole-free, polyphenylene oxide polymeric films.
It is also an object of this invention to prepare free-standing, polyphenylene oxide films having thicknesses of 400 angstroms or less.
These and other objects are obtained by the products and process of the present invention.